Virtualization and central coordination in wireless networks

ABSTRACT

A method for cellular network operation includes establishing communications in a cellular network between a given user equipment (UE) and a base station via a radio transceiver point (R-TP) that is associated with the base station. A virtual machine (VM), running on a virtualization platform (V-TP) that is associated with the cellular network, is assigned to perform at least a part of the Layer 2 processing functions in the communications between the given UE and the base station. A central coordinator makes a decision with regard to a division of the Layer 2 processing functions between the R-TP and the VM that is to be applied to the communications between the given UE and the base station, and conveying the decision to the R-TP and the VM, and the Layer 2 processing functions are performed in one or both of the R-TP and the VM in accordance with the decision.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication 62/214,996, filed Sep. 6, 2015 and of U.S. ProvisionalPatent Application 62/263,624 filled Dec. 5, 2015, which areincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates generally to digital communication systems and inparticular to cellular systems using a central coordinator and thevirtualization of part of base station functions.

BACKGROUND OF THE INVENTION

New technologies, as network functions virtualization (NFV) and softwaredefined networks (SDN) have positive elements which reduce thedeployment cost of the network elements, for example routers andswitches.

NFV application to cellular networks was studied recently in the SmallCell Forum and NGMN Alliance.

SDN was applied to WiFi networks in different demos, based on thefeatures and management interfaces of the IEEE 802.11a and IEEE 802.11kamendments. Based on these, an SDN Controller can allocate the power andselect an operational channel.

3GPP LTE standards were designed for the distributed operation of thebase stations and the CoMP (Collaborative Multi Point) standardizedfeatures were defined for distributed operation. The LTE architecture inRelease 13, pictured in 3GPP TS 36.300 V13.0.0 (2015-06). FIG. 4-1 inthis document does not include a Central Coordinator.

However some support for centralized coordination of inter-cellinterference was introduced in LTE Release 12, but even in LTE Release13 this support is limited only to a hypothesis on the assignment oftime-frequency resources which should be protected by another basestation, with no guarantee that the assignment will be indeed applied.

The limited support in 3GPP TS 36.423 Release 13 for centralcoordination has resulted in a high volume of measurement information,frequently above the up-link capacity of the VDSL base station backhaul.

In research papers appears the notion of network graph, presenting thewireless connection between different nodes as a visual characterizationof the wireless network interactions.

As both the term “controller” and “coordinator” are used in the wirelessindustry, it is needed to clarify the difference between them: the“control” is defined as an activity to determine the behaviour of anetwork element. The “coordination” is defined as an activity to enablethe efficient operation of the control functions, being situated at alevel higher than the “control” of a network element.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings do not represent an exhaustive representation of thepossible embodiments of the invention and the invention is not limitedto the arrangements presented in the drawings.

The drawings are:

FIG. 1—Represents the system architecture

FIG. 2—Represents a user equipment block diagram

FIG. 3—Represents a base station block diagram

FIG. 4—Represents a computing platform.

DETAILED DESCRIPTION

The following description is focused on the interactions between aCentral Coordinator and different entities of a heterogeneous wirelessdeployment. The interactions include reports which enable bettercoordination of the wireless network operation. The interactions aredefined so as to tolerate some delays which can appear in realdeployments.

Coupling Loss and Network Graphs, as described in PCT patent applicationPCT/IB2016/054313, which was filed Jul. 20, 2016, and is incorporatedherein by reference, are used throughout this description.

Embodiments of the invention are described hereinafter in conjunctionwith the figures.

The following description uses terminology familiar to those skilled inwireless cellular networks and in particular in LTE technology. Thisshould not be considered as a limitation for the applicability of theinvention to other similar technologies or to evolving cellulartechnologies.

eNB or base station denotes all types of base stations, using anytechnology, including macro, micro, femto or home base station, smallcell eNB, relays, remote radio heads, in distributed or centralizedarchitecture, including C-RAN architecture.

In this document an R-TP (Real Transmission Point/Radio TransceiverPoint) or simply TP may indicate a non-virtualized part of a basestation and also a non-virtualized full base station and may be namedalso “node”.

A Central Coordinator is a software module placed on a base station, ona server located at the network edge (routers, etc.), on Internet, inthe core network, in the Operation and Maintenance (O&M) system or on avirtualization platform.

A cell is a partition of space and frequency resources, identified by acell identifier.

The system architecture is described in FIG. 1, which includes the CoreNetwork (CN) including P-GW-101 (Packet Data Network Gateway), S-GW-102(Service GW, transferring user data between the Core network and theserving node), HSS-103 (Home Subscriber Server), the AdministrationServer-104, MME-105 (Mobility Management Entity) and the special IMSServer-106. The RAN (Radio Access Network) is represented by the CentralCoordinator-110 (CCord). R-TP1-121, R-TP2-122, R-TP3-123, at least onelegacy (non-virtualized) base station NVBS-124, the virtualized part ofthe one or more base stations (V-TP), including virtual machines namedVM1-131, VM2-132 and VM3-134. The R-TP1, R-TP2, R-TP3, includingantennas, are real transmission points or radio transceivers points ofthe one or more base stations. The base station NVBS-124 is also anR-TP, as includes antennas. The virtual machines are controlled by a VMController-140. The UEs, including UE1-151, UE2-152. UE3-153, UE4-154and UE5-155 are connected over the air to the serving base stationsthrough the Uu air interface.

While on each computing platform there is a Hypervisor in charge withcomputing resource management, we consider that is needed also a VMController, which controls the interaction between the wireless networkand the Hypervisor of the virtualization platform. The main task of theVM controller is the interaction with the Central Coordinator and withthe R-TPs on one side and with the Hypervisor of the virtualizationplatform on the other side.

The user data plane S1-U from the S-GW goes to VMs, hosting a number ofhigher layer UE-related data processing functions and some of theassociated control functions of the protocol layer. The routing of PDUs(Protocol Data Units) is done at the level of virtualization platform orper VM, to the destination R-TPs, identified by a TP-ID (similarly withBS-ID). The interface between a VM and R-TP is named C1 and transmitsuser data and radio control information.

In this way, some VMs host one or more of the RAN protocol higher layersrelated to the processing of the data for specific UE, and NOT relatedto one of the R-TPs. In this invention we prefer this approach given therelative long time and the load balancing problems related to migrationof an UE from a VM to another VM, as is the case in handover. The VMmigration takes place only in special cases, when is needed the VMmigration to a different virtualization platform. A Virtual Machinehandles the user data processing for one or more UE, for keeping thenumber of VMs scalable.

The traffic between S-GW and the serving VM, as well as the trafficbetween the VM and the R-TP should be tunneled; in an embodiment of thisinvention the same TEID (Tunneling End ID) could be used for all tunnelsto identify the same UE.

In one of the embodiments, if the UE is new in the coordinated area, theCCord authenticates the UE, allocates the TEID for all tunnels and sendsmessages to S-GW and surrounding R-TPs including the TEID and also theUE IP address which was allocated initially by the P-GW. In this way theUE can retain the same TEID in tunnels going to different R-TPs.

FIG. 1 also indicates a “cell margin” area, where the power of thewanted signal and interfering signals are similar.

In uplink, the interference is created by UE transmissions and isperceived at the serving eNB or at the R-TP of a specific UE.

The wireless access network can coordinate itself in a distributed mode,through the existing X2 interface, basically described in TS 36.423. Inthe centralized mode, we consider a C1-C interface, which could be inthe future part of the X2 interface or could be a stand-alone interface.As shown in FIG. 1, C1-C connects the CCord with the control functionswithin VMs, with R-TPs, with NVBS and with the VM Controller. Within theCN the CCord is connected to MME and in some embodiments also to S-GW.

Virtualization

Base station main functional blocks are PHY (Physical Layer) processing,Layer 2 processing including PDCP (Packed Data Convergence Protocol).RLC (Radio Link Control), MAC (Medium Access Control) sub-layersprocessing. Layer 3 processing (interactions with MME and S-GW throughS1 interface, X2 interface), interaction with O&M (Operation andManagement). In this invention the functions of Layer 1 and/or Layer 2may be grouped in a different way.

Within the entire cellular network there is a clear separation betweenthe control plane and user data plane.

In a virtualized approach, some functional blocks are moved on anexternal computing platform, consisting of processor(s), memory andeventual hardware accelerators. Parts of the processing resources of thecomputing platform are allocated to Virtual Machines (VM), where each VMhas a defined functionality. The VMs are managed by a Hypervisor, forexample Xen, KVM. VMWare, Hiper-V. The entire computing platformoperates under an Operating System, for example Linux or Windows.

The computing platform can be located in RAN, i.e. on one of the TPs, atthe edge, i.e. on a Router or on a standalone computer, or finally inthe cloud.

For sake of simplification we will consider that the computing platform,hence the VMs and hardware accelerators, are located at the edge of thecore network or access network.

Virtualization Platform Interactions with CCord

As already stated, the main task of the VM controller is the interactionwith the Central Coordinator, below are examples of CCord or R-TPinteractions with the VM controller.

Based on this invention, at installation, the VM Controller should beconfigured with the IP or Ethernet Address of the Hypervisor(s) and eachR-TP or the CCord should be configured with the IP or Ethernet addressof the VM Controller. The configuration is done either by O&M (Operationand Management System) or by the CCord.

Based on an embodiment, at first deployment an R-TP or the CCordcontacts the VM Controller and asks for the activation of a VM; as partof the message the R-TP or the CCord may indicate the required number ofprocessor cycles per sec, the size of the RAM and disk/non volatilememory. The VM Controller, depending of the actual used VM platform, cantransmit these parameters to Hypervisor or may ask the Hypervisor toallocate multiple VMs (to accommodate the R-TP or the CCordrequirements) or a combination thereof.

In response to this message, once the required resources were activated,the VM Controller will indicate to the R-TP or the CCord the IP orEthernet address of the allocated VM and the actual allocated resources.

A variant of this procedure is that R-TP or the CCord will specify theusage of the VM, for example through a bit-mapped IE, in which each bitrepresents a function or a combination of functions, for example PDCP,RLC, MAC. CRC (Cyclic Redundancy Check), Scrambling, Turbo-coding, etc.to be executed on the VM.

During the operation the R-TP or the CCord will send messages to the VMController for obtaining the status of resource utilization (average andpeak VM cycles/sec, amount or percentage of memory usage, HW acceleratorusage, etc.). In response, the VM Controller will indicate the requestedstatus.

During the operation the R-TP can go in a dormant state for some time.In this time the VMs should remain operational, as packets may arrivefrom the S-GW, but can work with reduced capacity. It should be notedthat deleting a VM and activating the VM on another platform is arelatively long process; this mode of operation should be avoided.

In the moment that user data or control messaging (as paging) arrivesfor a user served by a specific R-TP, the VM will alert the R-TP,indicating the target UE.

If an R-TP or the CCord needs more resources on the VMs, it can send areconfiguration message to the VM Controller. The VM Controller, basedon the actual available resources on different platforms, could satisfythe request on the same platform or could migrate the VM. As the VMmigration may be problematic (loss of packets, delays, etc.) at themoment of request, the R-TP or the CCord should indicate in the requestif VM migration is allowed and in which conditions.

If the R-TP or the CCord request may be satisfied without migrating theVM, the VM Controller returns positive response to the R-TP or theCCord.

The VM Controller can establish the operational context of eachcontrolled VM, such as one way or round trip delay, average and peakutilization of the allocated VMs, ingress/egress network traffic,average and peak memory utilization. This information can be transmittedto the associated R-TP or to the CCord at request or on a periodic basis(i.e. at fix time intervals).

The VM Controller can also indicate in a message the status of theentire platform, as overloaded, highly loaded, low loaded or on loadpercentages.

Based on this information, the VM Controller may request an R-TP or theCCord to reduce (if the VP platform is overloaded) the amount ofrequired resources, for example by partitioning the functional modulesbetween the R-TP platform and the VMs.

To this end the VM Controller may send to the R-TP or the CCord amessage containing a new bitmap which indicates a lower number ofoffloaded functions to VM.

In case of low load of the VM platform, the R-TP or the CCord may sendin a message a hypothesis, coded as a bit stream, for offloading morefunctional modules to the VM platform.

The VM Controller should set-up the software interface with theHypervisor of each selected computing platform, to monitor the usage ofVM resources, the latency between the R-TP and the allocated VM in bothdirections for each of the VMs or all VMs associated with a R-TP.

Routine Function

In an embodiment of this invention the routing function of the V-RP orof a VM sets a destination IP address and port/protocol based on theTP-ID provided by the CCord as an IE (Information Element) in itsmessages.

In LTE, the TEID is allocated for downlink by the base station and forup-link by S-GW; as in a network may be multiple MMEs and S-GWs and loadbalancing could take place between MMEs, implying core networkintervention, in this invention the Central Coordinator may become theentity which in a given area provides the TEID for each UE. This willsimplify the UE-specific interactions with the core network.

In the architecture in this invention the user data, after initialprocessing can be routed to one or more nodes, all the traffic being indownlink, as opposed to the existing dual-connectivity or network MIMO(Multiple-Input and Multiple-Output) solutions, where the user data issent through the up-link eNB backhaul. The message from the CCord to VMwill include identifiers of the target nodes (like TP-ID, R-TP ID orBS-ID). The VM Router will send the packet to the IP address of thecorresponding R-TP or BS.

It should be noted that in this invention the VM Router brings some S-GWfunctionality to RAN.

Functional Partition Between the R-TP and Computing Platform

At the time when the LTE architecture was designed, the user data wasdirected to a single eNB at a time, such that it was a strong linkagebetween eNB and UE; this link was disturbed only due to handover.

In the last years the increased UE traffic has justified the study ofapproaches such as dual connectivity and network MIMO; however thelimitations of up-link backhaul had to be considered and only dualconnectivity was reflected in standards.

A real backhaul may have a 1:20 uplink/downlink ratio, creating atraffic asymmetry which negatively affects the uplink transportcapability.

An additional characteristic affecting the performance when usingfunctional split is the backhaul delay and jitter, which may be too highrelative to the delay budget of the specific QCI (QoS Class Identifier)and to the delays of the radio interface.

Given the wired backhaul up-grade to VDSL (Very High Bit Rate SubscriberLine), the delay+jitter may be below 10 ms in a given region. At thisorder of magnitude it is possible to virtualize even the interactive RANlayers, such as RLC and MAC.

Part of the processing belonging to the LTE PHY layer, such as CRCcalculation, coding and scrambling, does not add significant traffic soit can be also executed on the computing platform. As an argument tosupport the above view, in some standards coding and scrambling areconsidered parts of Layer 2.

The round trip delay affects the H-ARQ process and the ARQ process.

A possible approach is the separation between PHY and higher layers. Inan embodiment of this invention the PHY Layer and some MAC and RLCfunctionality are located in R-TP, while the UE-specific data andcontrol planes are “virtualized” to an external computing platform.

VM Functional Pipeline

The VM appears as a pipeline of functional modules. For example, the DLuser data is processed in order in PDCP, RLC, MAC, etc. layers. Eachlayer may add a header containing a layer Sequence Number (SN).In UL, the data is processed in the reverse order: MAC. RLC, PDCP.In case that the packet resulting from a layer is too long relative tothe length of an IP packet, is needed a segmentation, with segmentnumbering, for transmitting the data.The last function in the VM DL chain shall be a routing function, withthe following functionality:

-   -   Inserts in the IP header the IP address of the target R-TP    -   Sends a packet to CCord including the last LSN of each included        Layer and the number of bytes in the UE specific queues, per UE        and per QCI.    -   The first function in the VM UL chain shall be a DPI (Deep        Packet Inspection) function, with the following functionality:    -   Retrieve the source IP Address and determine the R-TP ID of the        last correctly received packet    -   Retrieve the LSN of each included Layer in the last received        packet    -   Send a packet to the CCord including the retrieved information;        in this way the CCord will be informed about the status of        transmission/reception.        For detecting a bottleneck in the backhaul network, the R-TP        should also send the count of bytes in R-TP queues.

User Data Plane and Control Plane

In wireless systems there is a clear differentiation between the dataplane and control plane. In cellular technologies standardized by 3GPP,the control plane is referred to as “signaling” and take place at layer1 (Physical Control Channels), layer 2 (RRC-Radio Resource control) andlayer 3 (S1-C (control) and X2-C Interfaces.

The user data plane, named also user plane, includes the user data,connecting an UE to P-GW, while passing through S-GW. The IP packets inthe user data plane use GPRS Tunneling Protocol (GTP), making possibleto multiplex the packets to different UEs based on the TEID (Tunnelingidentifier) assigned to each UE. Additionally, the priority class ofeach packed is indicated by QCI (QoS class identifier). All packetsmarked with the same QCI form a bearer. An eNB groups the receivedpackets per UE and per QCI creating a queue for each UE and QCI. eNBflushes the queues in their priority order.The eNB controller considers the status of all UEs for assigningresources for downlink or uplink transmission. Based on the assignedresources, the queue status, and in downlink based on the last reportedCSI (Channel State Information) including CQI (Channel QualityIndicator) and/or RI (Rank Indicator), is created a Transport Block (TB)which is transmitted by the MAC Layer to the PHY Layer. For achievingthis, the UE data received from the S-GW has to be first processed bythe PDCP and RLC layers. It should be noted that the MAC Layer includesalso control functions (sometimes called high level MAC).

MAC layer operation depends on the actual RAT (Radio Access Technology),for example UTRA, E-UTRA (LTE), 802.11 (WiFi) and can be differentbetween the frequency bands, for example LTE frequencies lower than 5GHz and 5 GHz (LAA—Licensed Assisted Access).

The TB, including both data and signaling, is further processed by thePHY layer. According to 3GPP 36.212, V12.5.0 (2015-06), in downlink thefollowing PHY processing takes place in a sequential order:

-   -   a. Add CRC to the transport block    -   b. Code block segmentation and code block CRC attachment    -   c. Channel coding    -   d. Rate matching    -   e. Code block concatenation.

The next phase of data processing includes:

-   -   f. Scrambling;    -   g. Modulation scheme for generating a block of complex-valued        modulation symbols,    -   h. Layer mapping    -   i. Mapping to resource elements.

The IFFT provides the analog values to be transmitted over the air.

For different RATs the processing may be different, while someoperations can be very similar.

A similar processing takes place for the LTE PHY Control Channels.

Variants of Partition Between the Virtualized Platform and R-TP

Depending of R-TP capabilities, the following situations can beimplemented:

A. S1 and X2—Virtualized B. PDPC—Virtualized; C. PDPC and RLCvirtualized; D. PDPC, RLC, MAC virtualized; E. PDPC, RLC, MAC, andvirtualization of one of more of: CRC adding to TB. Code blocksegmentation and code block CRC attachment, Channel coding, Ratematching, Code block concatenation, scrambling, F. None (i.e. no VMused), allowing to transmit the user data from S-GW directly to theR-TP.

The decision of which kind of partition should be implemented depends onfactors like: available computing resources (computing cycles/second,memory) per VM, UE connectivity to one, two or more R-TPs, availablebackhaul capacity, etc.

For each kind of partition of the data plane operation, the messages ofthe C1 protocol should allow the transmission of specific controlparameters and user data between R-TP, V-TP (virtualized part of thebase station) and the Central Coordinator.

Central Coordinator

The Central Coordinator (CCord) executes the inter-node coordinationfunctions for a cluster of nodes in a geographic area, includingvirtualized and not-virtualized base stations. CCord collects reportsfor deciding the behavior of network nodes.

The coordinated nodes may be TPs of a single base station and/ormultiple base stations.

The inter-node coordination can address:

-   -   a. Load balancing    -   b. Mobility    -   c. Power levels of DL or UL transmissions    -   d. Time-frequency resource allocations for UE transmission,        where time may refer to time-slots or subframes, while frequency        may refer to a frequency channel, a group of frequency channels        belonging or not to an operator, a sub-division of a channel        (PRBs, subbands, etc.)    -   e. Time-frequency resource allocations for reference signals    -   f. Coordination of protected resources    -   g. Operation in Network MIMO transmission modes    -   h. Operation in multi-connectivity transmission mode    -   i. Medium access in un-licensed bands    -   j. Spectrum sub-licensing    -   k. Inter-operator infrastructure and/or spectrum sharing.        Below are detailed a number of messages supporting the above        functionality.

C1 Interface

The first operation is the set-up of the C1 interface. Assuming that theCCord IP address is know from an O&M configuration or can be discovered,the C1 set-up will be initialized by each control block in a VM and byeach R-TP.

At set-up interaction with CCord each VM should include its identifierand its capabilities in terms of supported UE IDs (it should be an UEidentifier at a level higher than C-RNTI (Cell Radio Network TemporaryIdentifier), possibly an X2 UE Identifier, supported layers andsupported functionality. The message can be built as a bit-map (string)or as enumerated entities.

A special situation is when the MAC control and/or RLC control is split,i.e. part of control functions are done in R-TP, part in VM and part inCCord.

Below are some examples of control messages sent by the different nodesin the network.

Messages Regarding the Functional Split of Control Functions

The functionality of each MAC, RLC, DHCP and RRC (Radio ResourceControl) protocol layers is specified at this time in respectively 3GPPTS 36.321 V12.6.0, 2015-06, TS 36.322 V12.2.0, 2015-03, 36.323 V12.4.0,2015-06 and TS 36.331 V12.6.0, 2015-06.

For supporting the control partitioning, in an embodiment CCordtransmits to the base station or to the VM the list or bitmap of thecontrol channels to be supported by each control entity in the R-TP orin the VM. The list can be provided separately per protocol layer andcan include only partial information, to be specified. For example: DCI(Downlink Control Information) sent in LTE over the air to UE, may becomposed from information provided by CCord, such as time/frequencyallocations and maximum transmitted power, however the modulation and/orcoding scheme can be selected by the R-TP, in line with real-timewireless propagation channel fluctuations. Other examples when CCordspecifies partial control information are the System Information Blocks,where part of information can be configured by O&M and part ofinformation can be dynamically configured by CCord.

In such a partition case, a bitmap or a list of IEs (InformationElement) will indicate to each VM or R-TP which are the IEs provided byCCord.

In the actual operation, a message sent to each R-TP or by IP multicastwill indicate the actual control data to be provided to MAC or PHYlayers for transmission.

In an embodiment, a correlation IE should be provided such that the R-TPwill know the relation between the received TB (Transport Block,carrying user data and eventually control data) from the VM and anallocated time-frequency, power, modulation scheme and transmit mode tobe used by R-TP.

The correlation information should be sourced by CCord and transmittedto the R-TP together with the allocation information and transmitted tothe VM together with the indexes of the logical channels assigned to beincluded in a TB which will be transmitted in that allocation.

In such a case the correlation information may be part of the messageheader.

Alternatively, both the R-TP and VM receive from CCord messagesinstructing which logical channels or data radio bearers to be includedin a TB are. The TB will be transmitted in a specific time-frequencyresource. If the partition is such that the MAC is executed by R-TP, theindex of RDB (Radio Data Bearer) and the index of the control channelshave to be included in the VM-transmitted packet headers.

R-TP will execute a DPI (Deep Packet Inspection) for determining whichlogical channels are included in a packet or TB and will transmit the TBin the assigned resource or will forward the packet to the suitablequeue.

Because the TB is formed by concatenating different RLC segments, theresulting block may be too long for an IP packet. So each segment or fewconcatenated segments shall be sent from/to VM to R-TP as one IP packet.

HARQ and ARQ

Another example of partition is related to handling of HARQ and ARQprocesses; given the possible inclusion of RLC and MAC layers in VMs,the type of redundancy (how many retransmissions) can be provided by theCCord. The actual TB building, such to include in the MAC or RLC headerthe retransmission index, can be handled by R-TP. With other words, theVM may provide only one block of data per R-TP, while each R-TP maybuild for itself the redundant versions with the appropriate header.This involves that in an embodiment where the redundant packets arebuilt by the R-TP, adding the CRC to the TB is a function of the R-TP.

Another possibility of functional partition is that the VM provides allthe possible CRCs, one per re-transmission, but only one data packet.The R-TP does not compute the CRC by itself, but appends at eachretransmission the suitable CRC.

In relation to ARQ, the UE sends a status report indicating the missingpackets or fragments. This information arrives first at R-TP and may beforwarded to VM. The R-TP or the VM, based on the stored information,can build the TB for re-transmission. If the VM does this, the delay ishigher.

CCord, function of real-time delay and jitter measurements and alsobased on information regarding the VM loading and processing delay, candecide where the TB formed with the packets due for retransmission isformed: at VM or at R-TP.

From the above discussion results that a message should be transmittedby the VM or by the VM platform controller to the CCord, indicating thedelay and jitter between virtualized UE-specific entities (RLC, MAC,PDCP) and each relevant R-TP. For reducing the amount of information, incase that multiple UEs are handled in the same VM, the CCord should beprovided by the VM Controller with the information, for each VM ID (VMIdentifier), of the processed UEs per VM. In such a case, the delay,jitter and load information can be provided per VM.

Use of Resources

An R-TP or a base station can report to CCord the use of resources percell as a summary or per selected granularity of the time/frequencyresources.

Each R-TP or base station or UE report to the CCord (Centralcontroller/coordinator) the supported cells, by indicating their centralfrequency (in kHz/MHz or as a code) and the channel bandwidth (inkHz/MHz or as a code).

Scheduling and Reporting Granularity

For example, in LTE the scheduling granularity is in general 1 ms(subframe duration), while the frequency granularity is a PRB (physicalresource block) or a subband or a full channel.

To transform this information in a RAT-independent mode should bementioned the time granularity e.g. 1 ms, 0.9 ms, LTE_full_subframe, andthe frequency granularity (e.g. 180 KHz, LTE_PRB. LTE_Subband,LTE_reduced_subband, etc.).

Alternatively, the subframes could be, as in LTE, defined by the systemframe number and the subframe number. This allows, for synchronizednetworks, a practical good time reference based on the absolute time.

Total Number of Resources Per Cell

The total number of frequency resources per cell is indicated whileusing one of the possible frequency granularities.

Another information of relevance is the number of transmit antennas andthe number of receive antennas.

Summary of the Resource Usage/Availability Per Cell

The summary of the time-frequency resource usage can be reported toCCord based on a number of steps as:

-   -   Number of used non-restricted resources, i.e. the resources        which are not restricted from p.o.v of transmitted power or        non-protected resources;    -   Number of fully restricted resources (or fully protected        resources), i.e. resources with transmitted power below a        threshold;    -   Number of medium restricted resources (or medium protected),        i.e. resources below a second threshold higher than the first        power threshold.

The summary of the available resources per cell, necessary for nodeselection or scheduling, can be presented as:

-   -   Number of available non-restricted resources, i.e. the resources        which are not restricted from p.o.v of transmitted power;    -   Number of available fully restricted resources, i.e. resources        with transmitted power below a threshold;    -   Number of available medium restricted resources, i.e. resources        below a second threshold higher than the first power threshold.

Function of the number of defined power levels (as absolute value,relative value, thresholds) the resource usage/availability per cell mayalso have more or fewer steps.

The resource usage/availability for different power situations can bepresented also as a percentage of the total resources.

Detailed Resource Usage Reporting

The detailed resource usage or the detailed available resources can bereported as a bitmap in time frequency domain, where for eachtime-frequency resource is reflected the type of resource, for example:available or used, fully restricted, medium restricted or notrestricted.

Protected Resources in LE (License-Exempt) Bands

The LBT (Listen Before Talk) in WiFi, used also in LTE mode named LAA(Licensed Assisted Access) is also a form of protection, given that onlyone transmitter on a channel will use the channel when the receivedsignal is higher than a threshold. In case that such a transmissiontakes place, the other potential transmitters shall use the resource ina fully restricted mode.

The available resources are those in which the level of energy is underthe LBT threshold in a defined percentage of operating time.

Allocation of Time-Frequency Resources

Allocation of time-frequency resources to a specific UE will includesome of the IEs indicated below:

-   -   a. The identifiers of R-TP and UE    -   b. DL or UL    -   c. In some embodiments per UE application or differentiated        between control and data    -   d. Per allocated frequency channel:        -   i. Allocated time-frequency resources (per subframe and            (PRB, group of PRBs, subband, etc. or as a bitmap of            frequency resources per subframe)        -   ii. If persistent scheduling, the repetition interval in            time domain

B. Allocation of power resources (DL or UL) for a specific UE willinclude some of the IEs indicated below:

-   -   a. The identifiers of R-TP(s) and UE    -   b. DL or UL    -   c. Per UE or per UE and QCI groups; two or more QCI groups can        have the same allocated power    -   d. In some embodiments per time and/or frequency dimension

The following information should be included per allocated frequencychannel:

-   -   a. Allocated time-frequency resources per subframe and per one        from the list of (PRB, group of PRBs, subband, etc. or        alternatively as a bitmap of frequency resources per subframe    -   b. If persistent scheduling, the repetition interval, in time        domain, of transmissions    -   c. The power level, indicated as zero power (muting), or        indicated relatively to one or more predefined thresholds, or        indicated as maximum power, or derived based on a request for        the protection of time-frequency resources in another cell.

The power level may be below a threshold in inter-cell interferencecoordination.

The size of the time-frequency resource shall be communicated by theCCord, through an IE, also to the RRC layer in a VM; based on this andalso on the selected modulation scheme the VM can build a TB.

The CCord makes its scheduling decisions based on information including:

-   -   a. Buffer status per UE and QCI, as reported by UE serving VM or        by R-TP;    -   b. Power headroom reporting—from R-TP for itself or for the        served UE;    -   c. RLC mode type as recommended by RLC: transparent,        unacknowledged and acknowledged.

Summary of Network Graphs Based on Coupling Loss

Given the use of Coupling Loss in the following description, we providea short summary of the main principles in the patent applicationPCT/IB2016/054313 filed Jul. 20, 2016.

Each vertex in the network graph represents the attenuation of thesignal transmitted by an antenna, presented in a linear form. Forobtaining the attenuation is needed to use the measured power of thereceived signal. The attenuation is obtained by dividing the power ofthe received signal, as reported by the receiver, to the power of thetransmitted signal, as reported by the transmitter. The received signalfrom a single source can be estimated from reference signals, forexample CSI-RS non-zero-power and zero-power in LTE or preambles inWiFi.

When the power of the future transmitted signal is known, it is possibleto compute the power of the resulting wanted signal by subtracting fromthe power received from a non-zero reference signal the power in a muted(zero power) reference signal.

The total interfering power can be computed by summing the power of theinterference power from each relevant transmitter and taking intoaccount its statistical behavior.

The statistical behavior of the received signal from each transmittertogether with receiver parameters can be used for deriving the expectedCQI (Channel Quality Indication) or the MCS (modulation and codingscheme) for a given probability of error. In case that the receiverparameters (noise factor, demodulation error, etc.) are not known, it ispossible to calibrate the system based on the CQI estimated by an UEused as receiver in given interference conditions.

Allocation of Modulation Scheme

The allocation of modulation scheme, a MAC Layer function, can be donebased on CSI/CQI reports or based on the MCS (Modulation and CodingScheme) deduction from the interference graph.

CCord can allocate the modulation scheme only or the full MCS (includingthe coding rate) based on the last CQI reports from UE. It should benoted that the CQI assessment by UE takes into consideration also thewireless channel statistics, firstly because it cannot be separated fromthe SINR measurements and secondly because it is requested by standardsto report the lowest CQI for a 10% error rate.

When using Network Graphs, the statistical channel information can beassessed in several modes, where the modes using R-TP or UE reportingrequire messages from UE or R-TP to CCord:

-   -   A. Inferring it from the historical variations of the parameter        represented by the edge line of the network graph, i.e. the        coupling loss;    -   B. Reported by the UE as mean and variance of the coupling loss        over a time interval;    -   C. Reported by UE as representative points of the CDF obtained        through measurements of the coupling loss, for example mean,        median, 90%, 95%;    -   D. Reported by the R-TP as mean and variance of the coupling        loss over a time interval;    -   E. Reported by R-TP as representative points of the CDF obtained        from UE reports of the coupling loss, for example mean, median,        90%, 95%.        CCord can configure the timing of the reports (periodical        interval or at request).

Based on the statistical properties of the coupling loss and also basedon the assessment of background interference levels, to be reported byUE, CCord can assess the MCS or only the modulation scheme for newcombination of transmission powers.

While the above description refers to DL, in a similar mode can CCordcan assess the MCS or only the modulation scheme for the uplink or forD2D (sidelink).

Based on time-frequency allocation and at least the modulation scheme,an R-TP or a VM can calculate the size of the TB and, if needed, thecoding rate.

Partition of Responsibility for Resource Allocation

The resource managed by CCord can be only part of the total availableresource; in this case a message should be sent to the involved R-TPsindicating by a bitmap the time/frequency pattern PRBs or groups of PRBsor subframes or frequency channels or groups of frequency channels(repetitive or not) of resources reserved for the central control byCCord.

CCord can allocate first the time/frequency and power resources to UEshaving prioritized packets; the first allocation can be done in such away to minimize the DL or UL interference between these resources.

Handover

Handover (HO) involves changing the serving R-TP for a given UE. Thisaction is initiated by UE or by the network.

In the existing LTE architecture, after being instructed by the servingeNB, a UE attempts to associate with the target eNB; once the handoverfinalized, the target eNB informs the MME, over the S1 interface; theMME commands the S-GW which will send the user data to the target eNB.

In our architecture the CCord can initiate the handover. If the servingR-TP has initiated the handover, the serving R-TP announces the CCord.

In case that UE is served by multiple R-TPs, the UE can remain connectedand receive/transmit data to one or more R-TPs during the HO process.

In all cases above, CCord asks the VM serving the UE or the Routingfunction through a message to stop sending data and control informationto the old serving R-TP; the incoming user data will be buffered on thecomputing platform. CCord will establish which are the new target R-TPsand will send a message to the specific serving R-TP(s) for connectingto those target R-TPs and to transfer the data and/or the controlinformation which was buffered in the meantime. Alternatively, thebuffered data can be transferred from the user serving VM to the targetR-TP or base station.

It should be noted the particular case when the HO implies an R-TP of avirtualized base station and a non-virtualized base station, while theuser data of the UE passes the virtualization platform. Using theprotocol layer splitting allowing no processing of UE traffic on thevirtualization platform, suitable for the NVBS, it is possible toexecute the HO between base stations with no involvement of the S-GW.

Energy Consumption (Energy Graph)

The traffic scheduling should be done in such a way to minimize theoverall energy consumption.

When selecting a serving node, CCord needs to consider the overallconsumed energy; for example, blanking of time-frequency resources willreduce the energy consumption of both the transmitting node, as can usehigher MCS, and of the blanking node, which will transmit zero power.This energy reduction will be done by spending more spectrum, such thatin practice may not be always possible.

For an UE in the active state the transmission-related energyconsumption, excluding the energy required by the general computing,will depend mainly on the radio used power and the time of transmission.

For an UE the relevant parameters are:

-   -   a. Total transmission power on all the used antennas    -   b. Time of transmission.

So for uplink should be selected serving radio nodes with the lowestpath loss or coupling loss and time-frequency resources less affected byinterference.

The serving eNB can schedule the actual resources for transmission,while the CCord can coordinate resources to be used in Network MIMO ormulti-connectivity; in the last case is not needed that thetransmissions to different radio nodes will be executed in the sametime.

For the network to UE transmission there are more parameters which caninfluence the receiving radio node selection and the appropriate RAT.

For example in a heterogeneous deployment the macro base station signalmay be stronger than a small cell signal, however the energy cost fortransmitting the same throughput can be much higher for a macro basestation due to:

-   -   air conditioning    -   losses in cables between the base band enclosure and the        antennas    -   higher distance to UE    -   powering up or down a specific radio node.

For providing an energy-efficient solution, the radio-node selection byCCord should consider parameters provided through a message by the basestation or by the radio node including:

-   -   the background (due to computing and air conditioning) consumed        power    -   the consumed power for each additional W of radio transmission.    -   the consumed power for powering-on the radio node.

The base station or the CCord should assess, for each potential radiotransmission node, the needed transmit power based on:

A. Transmission power of the reference signals

B. UE measurement reports (RSRP, RSRQ, CQI, MIMO rank, etc) or based onthe network graph assessing the CQI and MIMO rank.

C. the energy cost of powering up a radio node.

In addition, different RATs may have different peak-to-averageproperties which influence the consumed power, so the assessment shouldbe done per RAT. Also the operating frequency influences thetransmission power, such that the evaluation should take intoconsideration the suitable cells.

Of course, the smooth mobility and coverage requirements may justifyspending more energy, such that this aspect should be also consideredwhen selecting the radio transmitting or receiving nodes.

Based on the overall evaluation, the CCord will assign through messagesthe radio node(s) for serving the UE, the CoMP mode, the operation ofthe VM router or S-GW, through MME or directly.

UE Service Requirements and Radio Node Selection

An UE may run in the same time different applications, each one havingdifferent service requirements. Not all the available RATs will be ableto satisfy all the service requirements of the different applicationsrunning on an UE.

Each application may work with multiple parallel threads, while onlypart of the application threads may have special requirements on delay,throughput/user perceived throughput, resiliency, security, QoE (Qualityof Experience).

For allowing suitable routing to a radio node and scheduling of thetransmissions, the application should indicate through a message to thecontroller the radio node or to CCord which are the IP addresses(including port or protocol number) of the relevant application serverand/or client IP addresses, and for each IP address which are therequirements (average throughput, resiliency level, eventually maximumand or minimum throughput, average, minimum or maximum delay) apply forthis address.

In the defined messages the actual IP address can be replaced by anidentifier.

Alternatively, if a device behind a radio node is not identified by anIP address, but by a text having a known location in a protocol messageheader, the text length and the location in the protocol header shouldbe either fix or indicated by an IE (Information Element) in a message,together with the associated requirements.

An UE should provide, through a message to the radio node controller orto the CCord or to an entity in the core network (MME. Gateway), anoverview of its requirements, considered valid until changed, bygrouping the requirements in classes (each class being identified by anindex), indicating the traffic for each class and indicating theaddresses (IP or text-based or identifier-based) of the transmittersand/or receiver associated with each class.

The classes can be built based on technical requirements or based onNetwork Slices.

A base station or a serving radio node can further combine the trafficrequirements from different UEs before reporting them to higherhierarchical network controllers, like CCord, or to control (MME) oruser-plane (gateways) entities in the core network or to the OAM system.

The role of the network controllers, as CCord, is to analyze theserequirements and to assign the suitable radio nodes for uplink and/ordownlink communication for each mentioned address.

For example, a road safety application may require a latency of max. 5ms and a throughput of 100 Mb/s for transmitting un-compressed video toa car, the un-compressed video being generated by a camera connected toa video server located in the nearby of the road, and connected to anentity at the edge of the access network. In the same time the UE in thecar may receive infotainment traffic from a server in a cloud, with alatency requirement of 100 ms and a data rate of 20 Mb/s.

The UE sees a number of base stations and R-TPs, but not all of them aresuitable for transmitting the low-latency traffic. The CCord instructseither the S-GW (directly or through MME) or the VM (Virtual Machine)where the user data is pre-processed to route the low latency traffic,identified by the UE IP address and port/protocol, to the best availableradio node which supports a RAT able to support its requirements oflatency and traffic throughput.

In addition, CCord can select the appropriate cell or, if CarrierAggregation is used, cells, for serving this demanding traffic. Thenon-demanding control information may be identified by another addressand routed through the same or a different radio node.

The infotainment traffic can be routed to the same radio node or toanother one; the traffic may be identified by UE IP address and the usedports or alternatively by the infotainment server IP address.

In the above example the relevant video camera can be selected by theapplication server based on the position of the car and the car movingdirection. The video camera can be named by including its mounting placeand direction, for example “Camera on street Central no. 123 directionNord-South”. This text can be used as a field (IE) in a message forrouting its traffic to the serving radio node.

For implementing the actual traffic routing, a DPI (deep packetinspection) function should be supported by the S-GW or by the VM or theVM platform.

Estimation of Transmission Power and Available Capacity Per UE

When attempting to find one or more serving cells for a specific UE isneeded to assess the match between the RATs and frequency bandssupported by both the UE and the potential serving radio nodes.

The next step will be to determine the throughput or capacity requiredby the active applications and their QoS/QoE expectations.

Alternatively, based on the available resources in the radio nodes, theUE can be informed by the CCord which is the capacity of the accessnetwork for different classes of traffic. In turn, the UE can informeach application server on the possible throughput and delay.

For the matching relevant cells, separately for downlink and up-link,based on the number of the independent radio chains supported by UE andthe interference graph or based on the measurements indicating the CQIand the MIMO rank when single-user MIMO or Network-MIMO is applied, itshould be determined:

-   -   What is maximum user throughput and the delay that can be        achieved in each relevant cell while using fully protected        resources;    -   For the remaining traffic should be determined what is maximum        user throughput that can be achieved in each relevant cell while        using medium protected resources and which is the feasible        delay, in single-user MIMO or Network-MIMO modes;    -   For the remaining traffic:        -   How many physical resources are needed in the un-restricted            transmission mode;        -   What inter-cell CoMP procedures can be applied by using            resources in other radio nodes, for example:            -   Network MIMO

A message should be transmitted to the radio node controller and/or tothe CCord indicating the throughput (capacity) which can be scheduledper UE in each category of resource protection and which is the delayassociated with each category.

In response, the CCord can make the actual radio node allocation forserving each type of traffic of the UE and send messages to the VMserving the UE and to the serving radio nodes.

Paging

The UE will identify a number of R-TPs more suitable for communicationand will transmit, through a message to one of the R-TPs, the list ofthe suitable R-TP IDs. This list will be forwarded by the R-TP receivingthe message to CCord.

CCord decides one or several R-TPs to which the UE-associated VMtransmits the paging messages and transmits the information firstly tothe VM routing function and secondly to all involved R-TPs.

Broadcasting

The broadcasting from the virtualization platform can be directed to allR-TPs in an area or only to a number of selected R-TPs.

The CCord send through a message the list of relevant R-TPs to theUE-associated VM, such that the VM transmit the broadcast-relatedmessages. As part of the message header should be added the intendedabsolute time for transmission.

CCord also instructs the target R-TPs on the required service andprovides the time-frequency allocations for transmission.

Transmission Modes

CCord can also establish the transmission mode (TM) in a specifiedtime-frequency resource.

An IE is needed for including the TM index in a message including thetime-frequency information.

In case that separate messages are used, is needed a correlationinformation (assignment or allocation ID) to be included in differentmessages.

Multi-Point Transmission

The multi-point transmission to an UE can use the same time-frequencyresource for the involved nodes, exploiting the special propertiesthrough MIMO operation or can use transmissions using differenttime-frequency or frequency resources, with Carrier Aggregation (CA) ora combination thereof.

In the CA mode, the TBs to be transmitted on different carriers caninclude data or control information from one bearer, from multiplebearers or from a part of a bearer.

CCord will allocate the time-frequency resources and will control thebearer allocation per R-TP.

A correlation IE should be provided such that the R-TP will know therelation between the received TB and an allocated time-frequency, power,modulation scheme and transmit mode.

The correlation information should be sourced by CCord and transmittedto the R-TP together with the allocation information and transmitted tothe TM together with the index of the logical channels assigned to beincluded in a TB which will be transmitted in that allocation.

In such a case the correlation information may be part of the header.

Alternatively, both the R-TP and VM receive messages instructing whichthe logical channels or data radio bearers to be included in a TB to betransmitted in a specific time-frequency resource are. The transmissionprocess was described above.

Network MIMO (NetMIMO)

CCord can use the network graph to assess which R-TPs are suitable fornetwork MIMO; the criteria can be different for CS/CB (coordinatedscheduling/beamforming) as compared with multi-layer approach targetingincreased data rate.

As it can be found in literature, the measurements demonstrate that thecorrelation between different antennas is low in NLOS conditions,enabling high MIMO gains. A high coupling loss between a UE and R-TP mayindicate a NLOS condition with inherent higher delays. The high couplingloss can be correlated with the GPS coordinates or with positioningtechnology using positioning reference signals (PRS), on which ispossible to compute the actual distance. High coupling loss and lowactual distance indicate a NLOS condition.

At the same time a first UE can be in NLOS condition, i.e. with highcoupling loss, while a second UE can experience a low coupling loss.This means that the transmission to the second UE will not createsignificant interference to the first UE, such that is possible to useCS/CB.

Based on the coupling loss between the transmitting nodes and the targetUEs CCord can select the wireless nodes to transmit in the sametime-frequency resource and their transmission power.

In case that the CCord has detected a condition favorable for NetworkMIMO, the CCord will allocate the same time-frequency resource fornetwork MIMO to the cooperating R-TPs fulfilling the same condition andwill send a message to the selected R-TPs indicating a transmission modefor Network-MIMO, the R-TP IDs, the C-RNTP or other UE-ID, thetime-frequency resource as detailed above, the starting subframe fordata transmission, the subframe or the more general time-frequencyresource pattern for data transmission, the antenna ports to be used fortransmission and eventually the end of validity for this allocation. Themessage can include an identifier for this allocation, identifier to beused also in the communication of the CCord with the VM associated withthe UE.

In addition, the CCord should take additional measures for avoidingcollisions between the REs (resource elements) used for referencesignals and the REs used for data, given the fact that the mapping ofthe reference signals can depend on CellID. Such a measure can beallocating a common CellID for the time-frequency resource used inNetwork MIMO, such that the mapping of the data will be identical forboth R-TPs. This Cell ID can be identical with the CellID of one of thecells or can be a new parameter used in the mapping of REs used for dataand eventual of the REs used for some control channels. The selectedparameter used for mapping will be transmitted as an IE in a message tothe R-TPs involved in NetMIMO.

Another issue deserving attention is the avoidance of collision betweenthe PUCCH used by each R-TP. If the PUCCH is spatially multiplexed, thesame resource can be allocated for all the involved R-TPs. If this isnot the case, only one R-TP shall transmit at a time, all the collidingones being muted. The CCord shall transmit a message with an IEindicating the uplink mode of PUCCH allocation and the reservedtime-frequency resources.

Another CCord message will instruct, in downlink, the VM used by the UEto send the same TB to all involved R-TPs or to send different TBs tothe selected R-TPs, function of the selected NetMIMO mode. The messageshould include in addition to the NetMIMO mode the size of the TB andthe time-frequency allocation ID.

Function of the lower layers actually implemented by the VM, the VM willcreate data packets toward the selected R-TPs, including a field toindicate the allocation ID. The R-TP will send the packet in a queueintended for the assigned time-frequency allocation.

In uplink, the interference graph can indicate in a similar mode the UEssuitable for MU-MIMO. The CCord will send a message to the selected R-TPor VMs indicating which UEs can be scheduled in MU-MIMO mode.

The Net-MIMO transmit modes can include a high variety of modes. One ofthem can be used for interference cancellation at cell edge. Let's referto FIG. 1, where UE1 receives DB1 (data block one) from two of the fourantennas of R-TP1 and UE2 receives DB2 (data block two) from two of thefour antennas of R-TP2. In addition, R-TP1 creates interference to UE2reception and R-RTP2 creates interference to UE1 reception.

A Net-MIMO mode can comprise interference cancellation. For example,each remaining antenna of R-TP1 could transmit a signal which isessentially DB2, but which is rotated (phase shifted) and adjusted inpower such to cancel the interference induced to each antenna of UE1.

The network graph can be used for finding the coupling loss betweenR-TP2 and UE1; this coupling loss can be used for computing the transmitpower of the interference cancellation signal. The suitable precodingindex for each of the interference cancelling antenna can be provided byUE1, i.e. by the UE affected by interference.

We should observe that in LTE we have 8 transmitting antennas and 4receiving antennas. The reference signals for the desired signal shallbe separated in time domain from the reference signals used forinterference cancellation. A special configuration should be used fordetermining the precoding for the interference cancellation antennas, inwhich at a time transmit only the antennas creating interference and theantennas dedicated for the cancellation of this interference.

In total, will be needed three phases for determining the precodingrequired for the 8 transmitting antennas.

The CCord will also transmit a message to the interfering R-TPs,indicating a transmission mode for Network-MIMO, the R-TP IDs, theC-RNTP (see above) or other UE-ID, the time-frequency resource asdetailed above, the starting subframe for data transmission, thesubframe or the more general time-frequency resource pattern for datatransmission, the antenna ports to be used for transmission and theantenna ports to be used for interference cancellation and eventuallythe end of validity for this allocation. The message can include anidentifier for this allocation, identifier to be used also in thecommunication of the CCord with the VM associated with the UE.

The CCord will configure the VMs associated with each of the two UEs totransmit the same TB to each of the involved R-TPs. The IEs forcoordination of the VMs should include in addition to the NetMIMO modethe size of the TB, the allocation ID and the TP-ID to which the packetsshould be transmitted.

Function of the lower layers actually implemented by the VM, the VM willcreate IP packets toward the selected R-TPs, including a field toindicate the allocation ID. The R-TP will send the packet in a queueintended for the assigned time-frequency allocation.

Beamforming

The CCord can assess the possible MCS, while considering the processinggain achieved after coherent reception and the background interferencewhich can be calculated based on the network graph.

In case of beamforming, same TB will be sent by the virtualizationplatform to all R-TPs selected by CCord. In addition, theredundancy-related operation will be executed as explained above.

MIMO Channel Correlation Factor

The MIMO channel correlation above a certain limit conducts to the needof joint MIMO processing. This implies that the routing function of theVM will transmit by dedicated IP messages or by IP multicast the sameuser data, together with the indication of the assigned resource fortransmission as established by CCord, including also a precise timeindication, to the radio nodes involved in MIMO joint processing.

For each MIMO channel it should be added in the messages the informationrepresenting the correlation factor of the MIMO channel relative to allthe other MIMO channels relevant to co-located antennas or alternativelythe MIMO rank and the need for joint processing.

The CCord sends a message to each of the relevant radio nodes indicatingthe specific position in time/frequency domain of the reference signalsfor the involved antenna ports in each radio node, and eventually theblanked resources, to be used for assessing the channel correlation orthe MIMO rank or the need for joint MIMO processing.

As the position of the reference signals may be technology-specific, itwill be needed that during the evaluation of the channel correlation,MIMO rank and of the needed precoding the overlapping time-frequencyresources in the other involved technologies will be muted (zero power).

The MIMO channel correlation factor should be assessed for eachreceiving antenna of a signal from each transmitting antenna andreported through a message (signaling) to the radio node transmittingthe signal.

The radio node can further aggregate the information in a matrix or abitmap which can be transmitted to the CCord through a message. Each bitor group of bits in the bitmap will represent the channel correlation orthe MIMO rank for a group of antennas, representing the Network MIMO.The channel correlations can be represented relative to one or morethresholds, for example lower than 70% or equal or higher than 70%.

Additional thresholds can be added.

The message shall identify the transmitting antennas through theidentifier of the transmitting node and the port numbers of thetransmitting antennas, and the receiving antennas through the identifierof the receiving node and the ports of the receiving antennas.Alternatively, the position in the bit map can indicate the antennaports.

Coordinated Same-Time Transmissions in Un-Synchronized Systems

The LBT (Listen Before Talk)-based systems will not start thetransmission based on a scheduled approach, such that the absolute timeor derived time reference cannot be used. The same happens when thedifferent transmitters are not synchronized one to each other.

While based on LBT principles there is only one transmitter at a time,the network MIMO or other forms of CoMP (Cooperative Multi-Point) canstill be implemented based on the medium acquisition by one of thetransmitters involved in CoMP.

After the end of the previous transmission one of the radio nodes whichare part of a CoMP group (for example ReNB3) acquires the medium. At thebeginning of transmission or later on it sends a special signal orinformation which allows determining its identity. For example LTE cansend a cell identifier while 802.11 can send the source address as partof the MAC header.

The CoMP group is formed under the control of the CCord, which sendsmessages to each of the radio nodes for informing it which are the otherradio nodes involved in CoMP.

When another radio node in the same CoMP group (the above message mayalso include the identity of the CoMP group) receives the signal or theidentifying information, based on a message including a priory definedtime difference between the transmission of the signal or of theinformation and the start of the CoMP operation, this radio node maystart its transmission following the rules of the established CoMPoperation.

The start of transmission may be conditioned in some frequency bands bythe LBT (Listen before Talk) mechanism. If the medium is free, given therelatively high LBT energy threshold, coordination of transmissions canstill avoid interference at receiver.

If the medium is busy, and a radio node in the CoMP group detected anenergy higher than the LBT threshold produced by another node in theCoMP group, the LBT can be disregarded and the radio node can start thetransmission, because by applying CoMP the reciprocal interference willbe avoided.

The a priori defined time difference may be transmitted from CCordthrough a message which may also include the type of CoMP operation(Network MIMO-joint processing, Network-MIMO coordinated scheduling,power limitation of some transmitters in specified time-frequencyresources, etc.)

The coordination of transmission can be also done in a distributed mode,by sending the same type of messages from a transmitter to the othertransmitters.

Traffic Aggregation and Routine

For more efficient backhaul use and faster scheduling the traffic shouldbe aggregated, both in downlink and uplink.

The existing approach of tunneling per QCI (QoS Class Identifier) hasthe advantage of fast mapping of the existing DiffServ traffic marking(RFC 2474) to QCI. However there is no concatenation of the smallpackets over the backhaul.

In downlink, the virtualization of the user plane can allow theconcatenation of the small packets targeting the same UE and originatingfrom different application servers and having the same QCI into a singlepacket having as destination the UE serving radio node. Thede-concatenation can be done at the transmitting radio node or at theUE.

In uplink, the concatenation can be done by the UE or by the receivingradio node. In case of user plane virtualization, the virtualizationplatform can concatenate the packets with the same CQI which areintended to the same application server.

QoS Based Tunneling

The DifServ marking, which today is used for QCI-based tunneling, doesnot correspond anymore to the new QoS requirements, which can be by farmore stringent than those specified in 2015 for QCI. For example, theminimum delay can be in the order of few milliseconds, while in 3GPP TS23.203 the minimum delay is 60 ms.

In case of user plane virtualization, based on DPI searching forspecific addresses, it is possible to identify the packets which havemore stringent delay requirements than DiffServ/QCI marking. Thosepackets can be tunneled to the serving radio node with a new QCImarking, identified in the packet header by specific bit(s),corresponding to the new QCI (or a new name).

Alternatively, the DPI should be done at the serving radio node foridentifying the traffic with more stringent new requirements, based on alist provided by UE, OAM or CCord through appropriate messages.

Network Slices

Essentially each network slice has its own billing model.

The assignment to a network slice should be done based on the address ofthe application server or, in case of proximity services using dedicatedradio nodes, based on the address or ID of the serving radio node.

The UE or the serving radio nodes or the serving VM should send with amessage the IP addresses (including port number or protocol number) oraddresses associated with a text (name) of each application server orwith one or more dedicated ports of the radio node as allocated by thecontroller of the radio node or as configured by the OAM system, to theentities counting the traffic associated to a specific network slice:

A. Core network elements in charge of billing and routing

B. VM processing the user data

C. Radio nodes

The entities counting the bytes associated with each network slice willsend through a message the counting result for each network slice to thebilling entity. A specific network slice can be mentioned in a messageby an identifier.

When assigning resources to each network slice, the base station or theCCord should make sure that all the served UEs have assigned at leastthe minimum requested resources for operation. In this mode will besatisfied the operator requirement of isolating the network slices onefrom the other.

A more detailed accounting can involve, for each network slice, the QCIor the new QCI, the operator name (PLMN), the used spectrum.

RAN Sharing

In an embodiment shown in FIG. 1, on the virtualization platform the UEsserved by a specific Operator have a dedicated VM for the processing ofthe higher layers, while an R-TP can be shared by multiple operators.This is a form of inter-operator infrastructure and/or spectrum sharing.

For example, UE4 has a subscription with Operator 1; within thecomputing platform VM1-131 is allocated to PLMN1 (Public Land MobileNetwork) which is operated by Operator 1. VM2-132 is allocated to PLM2and will process the traffic from UE1-151 and UE3-153. However both UE3and UE4 can be served by the same R-TP1-121.

RAN Sharing Cost

A main advantage of RAN sharing is the availability of more radio nodesfor serving an UE, reducing by this the energy consumption andincreasing the peak data rates, especially when the spectrum is alsoshared.

However the cost of sharing should be taken in consideration. The costcan be function of the available resources and of the sharing time.

CCord can decide if the RAN sharing by a specific radio node can beaccepted by an UE belonging to another operator based on the currentcost of sharing of the radio infrastructure and of the cost of spectrum.

Based on a message from the CCord, a radio node will broadcast or notthe PHY signaling of support for a PLMN.

The cost of RAN sharing may also depend on the network slice.

UE Block Diagram

FIG. 2 shows the UE block diagram. The central radio control, includingthe functions related to the User Plane and Control Plane as describedin 3GPP TS 36.300 and radio activities, is located within a centralprocessing unit 202, which may also perform other high-layer userservices, including running applications.

The user interfaces, such as the display, speaker, and microphone, arelocated in a user interface block 201.

A memory block 207, containing RAM and non-volatile memory (FLASH orROM) is used by the central processing unit 202 and depending on theactual UE implementation, may be used also by the user interfaces 201.

Digital signal processing is performed by a signal processing block 203and can give services to the radios using FDD for communication, likeradios 204, for the cellular operation in licensed and un-licensedbands, and also to other radios-206, such as WiFi and Bluetooth,operating generally in license-exempt bands. Antennas 205 can be usedfor receive (RX) and transmit (TX), while using diplexers or switches toconnect it. If the receive and transmit radio frequencies are far fromeach other, however, different antennas may be used.

TP Implementation

The base station or R-TP blocks shown in FIG. 3 are only by way ofexamples; in practical implementations these blocks can be distributedon multiple circuit boards, and the control functions and hardwarefunctions can be implemented on commercial processors or tailor-madelogical arrays, such as system-on-a-chip. FPGAs, ASICs.

The functional blocks of the base station/R-TP-301 identified asrelevant to this invention are the radio interface 303, providingwireless communication with a UE, the network (communication) interface304 enabling message transmission over the network, towards another basestation or to the OAM or to a Central Coordinator.

The controller 302 includes as a subset of its functions, some functionsrelevant to this invention, such as scheduling of the reference signals,configuring and obtaining reports from an UE, including computingfunctions determining coupling loss or the path loss. The data used bythe controller is stored in a memory block-305.

Computing Platform

A computing platform 401 (see FIG. 4) is a system that consists of oneor more processors 402, non-volatile memory 403, volatile memory 405, anetwork communication interface-404 and a system controller 406. Anapplication, program or process runs over an operating system installedin the computing platform.

The computing resources of a computing platform can be dynamicallyallocated to one or more virtual machines, such that each virtualmachine can use a number of processor cycles and a partition of thevolatile and non-volatile memory.

Central Coordinator

The Central Coordinator includes one or more software modules, adaptedfor controlling the system nodes based on the received information.

The Central Coordinator defines, controls the system nodes and the UEand receive operational status information from virtualized ornon-virtualized base stations, UE and VM Controller.

The Central Coordinator includes hardware computing resources such asone or more processors, memory, communication interfaces.

The Central Coordinator may use dedicated enclosures or can run itssoftware on virtual machines or by other means for sharing resourceswith other software modules.

Technologies

As will be appreciated by those skilled in the art, the terminology usedthroughout the specification is mainly associated with the LTEstandards. However, it should be understood that embodiments of thepresent invention encompass other existing and future cellular standardsand other wireless systems used in terrestrial or satellitecommunications and both TDD and FDD duplexing modes.

The examples provided show certain ways of carrying out the invention.It is to be understood that invention is not intended to be limited tothe examples disclosed herein. Rather, the invention extends to allfunctionally equivalent structures, methods and uses, as are within thescope of the claims.

1. A method for cellular network operation, comprising: partitioning abase station in a cellular network into a virtualization platform andradio transceiver points; establishing communications between a givenuser equipment (UE) and the base station via at least one radiotransceiver point (R-TP) that is associated with the base station,wherein the communications include PHY (Physical Layer) processing,Layer 2 processing, including functions within PDCP (Packed DataConvergence Protocol), RLC (Radio Link Control), and MAC (Medium AccessControl) sub-layers; assigning at least one virtual machine (VM),running on the virtualization platform, to perform at least a part ofthe Layer 2 processing functions in the communications between the givenUE and the base station; making a decision by a central coordinator withregard to a division of the Layer 2 processing functions between theR-TP and the virtualization platform that is to be applied to thecommunications between the given UE and the base station, and conveyingthe decision to the at least one R-TP and to the virtualizationplatform; and performing the Layer 2 processing functions in one or bothof the at least one R-TP and the at least one assigned VM in accordancewith the decision.
 2. A method according to claim 1, wherein thedecision depends on the delay between the virtual machine processing theUE data and the radio transceiver.
 3. A method according to claim 1,wherein the decision depends on the backhaul capacity.
 4. A methodaccording to claim 1, wherein the decision depends on the virtualizationplatform or virtual machine processing capacity.
 5. A method accordingto claim 1, wherein the at least one assigned VM is not migrated in caseof handover of the given UE from one R-TP to another R-TP.
 6. A methodaccording to claim 1, wherein at least one but not all PHY processingfunctions are executed on the at least one VM.
 7. A method according toclaim 1, wherein none of the PHY, RLC and MAC processing functions isexecuted on the at least one VM.
 8. A method according to claim 7,wherein the R-TP is a non-virtualized base station.
 9. A methodaccording to claim 6, wherein at least one PHY function selected from alist consisting of: adding cyclic redundancy check (CRC) to a transportblock (TB), code block segmentation and code block CRC attachment,channel coding, rate matching, code block concatenation and scramblingis executed on the at least one VM, while the rest of the PHY functionsare executed on the R-TP.
 10. A method according to claim 1, wherein theuse of computing resources for user data processing by the at least oneVM assigned to the given UE is reported to the central coordinator or tothe R-TP serving the given UE.
 11. A method according to claim 10,wherein the reported use of the computing resources by the at least oneVM includes one or more of: one-way delay, round-trip delay, average andpeak utilization of the at least one assigned VM, ingress networktraffic, egress network traffic, average memory utilization, and peakmemory utilization.
 12. A method according to claim 1, wherein assigningthe at least one VM running on the virtualization platform is done at arequest by the central coordinator or by the R-TP serving the given UE.13. A method according to claim 1, and comprising sending a message fromthe central coordinator or the R-TP to a controller of thevirtualization platform to request allocation of more computingresources to the at least one assigned VM.
 14. A method according toclaim 1, wherein on the virtualization platform, UEs served by aspecific operator have at least one dedicated VM for processing ofhigher protocol layers, while an R-TP can be shared by multipleoperators. 15-27. (canceled)
 28. Apparatus for deployment in a cellularnetwork, in which a base station is partitioned into a virtualizationplatform and radio transceiver points and communications are establishedbetween a given user equipment (UE) and a base station via at least oneradio transceiver point (R-TP) that is associated with the base station,wherein the communications include PHY (Physical Layer) processing andLayer 2 processing, including PDCP (Packed Data Convergence Protocol),RLC (Radio Link Control), and MAC (Medium Access Control) processingfunctions, the apparatus comprising: a network interface; a memory; andat least one processor, which is configured to operate as avirtualization platform on which is implemented a part of the basestation, running at least one virtual machine (VM), and to receive, froma central coordinator, a decision with regard to a division of the Layer2 processing functions between the virtualization platform and the atleast one R-TP that is to be applied to the communications between thegiven UE and the base station, and to assign a VM running on thevirtualization platform to perform, responsively to the decision, atleast a part of the Layer 2 processing functions in the communicationsbetween the given UE and the base station.
 29. Apparatus for deploymentin a cellular network, in which a base station is partitioned into avirtualization platform and radio transceiver points and communicationsare established between a given user equipment (UE) and the base stationvia at least one assigned radio transceiver point (R-TP) that isassociated with the base station, wherein the communications include PHY(Physical Layer) processing and Layer 2 processing, including PDCP(Packed Data Convergence Protocol), RLC (Radio Link Control), and MAC(Medium Access Control) processing functions, the apparatus comprising:a network interface; a memory; and at least one processor, which isconfigured to serve as a central coordinator of the at least one R-TPand of the virtualization platform, wherein the at least one R-TP andthe virtualization platform are each able to perform at least a part ofthe Layer 2 processing functions in the communications between the givenUE and the base station, wherein the central coordinator makes adecision with regard to a division of the Layer 2 processing functionsbetween the at least one R-TP and the virtualization platform that is tobe applied to the communications between the given UE and the basestation, and conveys the decision to the at least one R-TP and thevirtualization platform which assigns at least one VM in accordance withthis decision.
 30. (canceled)
 31. Radio transceiver point apparatus fordeployment in a cellular network, in which a base station is partitionedinto a virtualization platform and radio transceiver points andcommunications are established between a given user equipment (UE) and abase station via at least one radio transceiver point (R-TP) that isassociated with the base station, wherein the communications include PHY(Physical Layer) processing and Layer 2 processing, including PDCP(Packed Data Convergence Protocol), RLC (Radio Link Control), and MAC(Medium Access Control) processing functions, the apparatus comprising:a radio interface; a network interface; a memory; and at least oneprocessor, which is configured to receive from a central coordinator adecision with regard to a division of the Layer 2 processing functionsbetween the virtualization platform and the said apparatus and toperform, responsively to the received decision, the Layer 2 processingfunctions assigned to the said apparatus in the communications betweenthe given UE and the base station, wherein the virtualization platformassigns at least one VM to perform, responsively to the decision, thecorresponding part of the Layer 2 processing functions.